Standard steel certification is currently to EN 10025.
A classification system using a series of numbers and letters is used to differentiate different types of steel. If you are contemplating building a shell, speak to your local steel stockholder.
Speak to your chosen shell builder
if you are interested in his steel spec. but really it’s probably best to trust his judgement.
For those of you really interested:
A common steel maybe classified under EN 10025 as being S 275JR
This is uncoded as:
S - Structural Steel
275 - A minimum yield strength (Reh) which measures stress loads as the material transitions from plastic to elastic
JR - relates to figures obtained from a Charpy v notch impact test
And that is why it is probably better left to your chosen experts to advise you on what is best for your project!
Typical steel thicknesses are:
10mm base plate
6mm hull sides
5mm cabin side
Therefore a canal boat built with same would be classified as being 10,6,5,4.